The Study of Magnetic and Magnetodielectric Properties on FeTe3O7X(X=Cl, Br)

• Main Authors: Yu-Kuan Yang, 楊育寬
• Other Authors: Hung-Duen Yang
• Format: Others
• Language: zh-TW
• Published: 2013
• Online Access: http://ndltd.ncl.edu.tw/handle/92966564418317881702

碩士 === 國立中山大學 === 物理學系研究所 === 101 === The Fe3+-Te4+-O-X(X=Cl, Br) system has Fe3+ ion to be the source of magnetism and Te4+ ion has lone pair to result in the charge distribution is not uniform, and it can be regarded as the reason which the system has ferroelectricity. We concentrate on magnetic and magnetodielectric properties on the antiferromagnetic spin dimer compounds FeTe3O7X(X=Cl, Br). The magnetic transition temperature appear about 102 K for X=Cl while it shows about 94 K for X=Br. From structure, one unique Fe3+ ion coordinate a [FeO5] trigonal bipyramid, and two such trigonal bipyramids have a common edge to form [Fe2O8] dimer units that are isolated from each other by Te4+ ions to form layer structure. In dielectric measurement, we can observe an interesting phenomenon above 300 K. At this temperature range, dielectric constant increase with increasing magnetic field below 20 kOe, but it decrease with increasing magnetic field above 20 kOe. At the same range, we can not fit magnetodielectric coupling constant, but it is indeed that dielectric constant change when we change magnetic field. Because magnetic transition temperature shows about 100 K, electric transition is above 300 K and we can not get coupling constant. We confirm that this system is not multiferroic material.